Electron discharge device



Oct. 22, 1940. o. s. LANGMUER 2,219,107

I ELECTRON DISCHARGE DEVICE Filed Aug. 29, 1959 INVENTOR. 04 W0 8.LANGMU/R ATTORNEY.

Patented Oct. 22, 1940 PATENT OFFICE ELECTRON DISCHARGE DEVICE David B.Langmuir, Engiewood, N. 1., assignor to Radio Corporation of America, acorporation of Delaware Application August 29, 1939, Serial No. 292,398

5 Claims.

My inventiorrrelates to electron discharge devices, particularly toseals and lead-ins for such devices.

The required large number of lead-in con- 5 ductors in many commercialtubes seriously com- In some plicates the manufacture of the tubes.cathode ray tubes, for example, the number of focusing and acceleratingelectrodes is limited by the number of Wires that can be sealed into thei stem at the end of the tube. Wires are difficult to seal into the sidewall of a tube, and the presence of even the ends of the wires on theinterior of the envelope distorts the focusing field of the ring-shapedelectrodes.

it! An object of my invention is an electron discharge device into whichany desired number of lead-ins may be easily sealed.

A more specific object of my invention is a tube of the cathode ray typein which a plurality of go coaxial ring-shaped electrodes with lead-inconductors may be easily made and in which the fields of the electrodesare undistorted.

The characteristic features of my invention are defined in the appendedclaims and a preferred 25 embodiment is described in the followingspecification and shown in the accompanying drawing in which Figure l isa sectioned view of a cathode ray tube embodying my invention and Figure2 is a detailed transverse sectional view of a 30 lead-in conductor ofFigure 1 constructed according to my invention.

The cathode ray tube chosen for illustrating the characteristic featuresof my invention and shown in Figure 1 comprises an envelope l with anelongated tubular portion joined at one end to a viewing plate 2internally coated with an electron responsive luminescent material 3 andclosed at the other end with a conventional re-entrant stem carrying anelectron gun 4. A beam of 4 electrons emitted from the inner end of thegun is directed toward the screen, the electrons being accelerated andfocused to a sharply pointed beam by the coaxial ring-shaped electrodes5. The focusing electrodes 5 may conveniently be 45 rings of metaldeposited as thin films upon the inner wall of the envelope. Directcurrent positive potentials may be applied to the ring electrodes tocause the beam of electrons emanating from the end of the electron gunto sharply 50 focus upon the screen.

The usual type of lead-in conductor for each ring electrode 5 compriseseither a separate wire sealed through the cylindrical side wall of theenvelope and soldered or otherwise ioined at its my inner end to thefilm electrode, or a wire ex tending to the electrode from the press atthe end of the envelope. The wire in either arrangement electricallydisturbs the smooth continuity of the inner surface of the cylindricalelectrode and distorts the electrostatic field with 5 a resultingdefocusing of the beam. Lead-in conductors for the electrodes, accordingto my invention, leave the fields of the inner surfaces of the ringelectrodes cylindrical in shape and the fields undisturbed.

The lead-in conductors, according to my invention, are made byperforating the envelope and by making one hole in the envelope oppositeeach focusing electrode. The holes may conveniently be made by heating atungsten wire white hot and pushing the end of the wire through theglass. The surface of the glass in the holes and on the inside andoutside of the envelope is then coated with a thin layer of metal sothat a continuous film of metal not only forms the electrode but alsoextends along and is hermetically sealed to the walls of the hole andcontinues to the outside where it forms an outside contact. Any metalwhich will form an adherent conductive film on the glass and also ahermetical seal to the glass may be used, although I prefer to use andhave obtained good results with the adherent conductive metal coatingproduced with a platinizlng solution such as that commercially known asLiquid Bright Platinum No. 05. The entire inner surface of the envelope,between the ends of the focusing region, may be coated with the metalfilm and the separate sections of the film electrically separated byremoving the film as with a lathe tool. Alternatively, of course, the asseparate ring-shaped deposits may be separately applied with suitablespraying and masking means. A narrow strip 6 of the metal film on theexterior of the envelope is extended some distance from the hole on theoutside of the envelope to form an exposed area of film to whichexternal contact may be made. Each metal-lined hole is then closed witha plug such as a bead of glass, which will hermetically seal to themetal film. The envelope is heated nearly to the softening point but notto its deformation temperature, and the end of a piece of caneglass,preferably of the composition of the envelope, heated until it is softenough to form a workable globule on the end of the rod, is pushed downso over and puddled in the hole in the hot envelope to fill and seal thehole, and the rod of cane glass pulled away. I have found that in thisway I can hermetically seal the metal film on the walls of the hole tothe glass plug andalso to the 66 envelope. As the envelope is below itsdeformation temperature the shape 01' the hole in the envelope is notchanged during the puddling of the glass head in the metal lined hole.Solder with the proper coeilicient of thermal expansion could,alternatively, be employed to close the leadin holes. After the holeshave been closed the tube may be exhausted and sealed oil in the usualmanner. Electrical connection is easily made to each of the focusingelectrodes with spring contactors 7 bearing on the exterior metal filmat each hole.

Since the lead-in conductor does not extend inwardly beyond the innersurface of the envelope the electrostatic fleld produced by theelectrodes is concentric with the axis of the envelope and the electronbeam, and there is no distortion in the field or in the beam. Since theouter diameter of the envelope is not increased, a close fittingdeflection coil may he slipped over the envelope. The exterior metalfilm for each lead-in may conveniently be extended toward the ends ofthe envelope to a point beyond the end of the coil.

By my invention it is easy and inexpensive to make an electron dischargedevice with a great number of lead-in conductors. Cathode ray tubes forexample may have a plurality of coaxial an- ,nular electrodes veryclosely spaced and in which the fields of the electrodes areundistorted, yet with ample spacing between lead-in conductors whichextend through the wall and may be staggered around the circumference ofthe envelope.

The lead-in conductors are of minimum length,

which is the thickness of the envelope wall, and are therefore of greatutility in very high frequency apparatus.

I claim:

1. An electron discharge device comprising a so glass envelope, aplurality of electrodes in said envelope, a lead-in conductor for eachelectrode, each electrode comprising a metal coating on the interiorwall of said envelope, a. hole in the envelope wall opposite eachcoating, and each conductor comprising an annular him of metal on thewall oi said hole and on the exterior wall of said envelope integralwith the coating of one of said electrodes, and a bead of glass sealedgastight in each hole.

2. An electron discharge device comprising an envelope of insulatingmaterial, a plurality 01 small spaced holes in the wall of the envelope,a plurality of electrodes in the envelope, a short lead-in conductor foreach electrode comprising 10 an adherent coating of metal on theinterior and exterior walls of the envelope electrically communicatingwith a metal coating on the sides of the hole, and a plug sealedgas-tight in each of said holes.

3. An electron discharge device comprising a cylindrical envelope ofinsulating material, a plurality of spaced holes in the cylindrical wallof the envelope, a metal coating on the sides of each hole, each coatingextending inwardly and outwardly along the inside and outside walls ofthe envelope, and a plug sealed gas-tight in each of said holes.

4. The method of sealing in a plurality of short lead-in conductors inthe side wall of a cylindrical envelope, comprising forming a pluralityof spaced holes through the wall of the envelope, depositing an adherentcoating of metal on the interior and exterior surfaces of the envelopeand on the sides of said holes, then heating a mass of sealing materialand depositing the heated mass in gas-tight union with the coated sidesof said holes.

5. The method of sealing a short lead-in conductor in the wall of anenvelope, comprising forming a hole through the wall of the envelope,depositing an adherent metal coating on the interior and exteriorsurfaces of the envelope and on the sides of said hole, the metalcoating on the interior and exterior surfaces and in the hole beingdeposited so that the coatings are conductively connected to form alead-in conductor, then hermetically sealing said hole.

DAVID B. LANGMUIR.

